Polymer-bonded material

ABSTRACT

A polymer-bonded granular adsorptive, absorptive, chemisorptive, or catalytically active material and a process for producing molded bodies from this material. An objective was to develop a polymer-bonded granular adsorptive, absorptive, chemisorptive, or catalytically active material which is capable of forming an open-pore and sorptive foamed body at increased temperatures while not reducing the specific surface of the active material and with a binding effect only during the mixing and processing phases, as well as a process for producing molded bodies from this material. This objective was met by mixing and processing an adsorptive, absorptive, chemisorptive, or catalytically active fine-grained material together with a finely particulate, meltable polyethylene with the addition of a binding agent having an oligocondensate basis.

This application is a divisional of application Serial No. 09/161,357,files Sep. 25, 1998, now U.S. Pat. No. 6,083,439.

FIELD OF THE INVENTION

The invention pertains to a polymer-bonded granular absorptive,adsorptive, chemisorptive, or catalytically active material, which isproduced by mixing the absorptive, adsorptive, chemisorptive, orcatalytically active fine-grained material with a finely particulatemeltable polyethylene with the addition of a binding agent having anoligocondensate basis (or backbone), as well as a process for producingmolded bodies from this material.

BACKGROUND OF THE INVENTION

Molded filter bodies with an adsorptive effect based on activated carbonare known in the prior art. The following substances are used asmatrices for the activated carbon:

open-pore foamed plastics

phenoplasts

polyurethanes

plaster of paris

paper substrates

carbon networks (or carbon backbone)

The basic principle underlying inventions of this type is that ofintroducing activated carbons into the polymeric body or of forming acarbon matrix integral to the activated carbon itself (DE Al 41 40 455).

The solution described in DE C2 37 19 419 uses open-pore foamed plasticas the substrate material.

DE Al 39 25 693 suggests forming a three-dimensional matrix out of thecarbon by coating it with a binding agent, but does not elaborate.

A similar solution is proposed in DE Al 38 135 64.

DE Al 41 40 455 describes a process for producing composite adsorbentswhich are characterized by high abrasion resistance and consist ofhighly porous inorganic filler materials and a chemically resistant andporous matrix. This is attained by carbonizing the water-soluble bindingagent, e.g. preferably pitch acid.

DE Ul 91 15 610 also describes foamed plastics, preferably well foamedpolyurethanes, into which the activated carbons are introduced.

According to EP Al 04 92 081, a mixture of cellulose, polyvinyl alcohol,and activated carbon is formed into a hexagonal body with a controlledpore size. The product is well suited for adsorbing aerial impurities,although it does not achieve satisfactory capacities.

DE Al 34 43 900 and DE C3 24 00 827 describe carbon-impregnated textilesand nonwoven fabrics. These solutions use special polymers with apolyurethane basis, e.g. polyurethane fluoride andpolytetrafluoroethylene urethane.

The Romanian patent RO 10 40 21 also describes a porous polyurethanesupport material containing granulated activated carbon in its pores.The granular material is produced by impregnation with a solution of 15to 20% activated carbon powder and 15% binding agent, which demonstratesthat these capacities are not satisfactory either.

Interesting processes for producing molded bodies out of activatedcarbon for use in gas masks are claimed in U.S. Pat. No. 5,078,132, EP03 09 277, and WO 94 03 270. These solutions describe a self-supportingporous gas filter material consisting of a molded body containingcharacteristically defined particles of the adsorptive material and thethermoplastic binding agent. The individual particles are fused into amolded filter body with open pores. It is characteristic of thesesolutions that the size of the binding particles is less than 20% of theaverage size of the adsorbent particles. The disadvantages are thatsatisfactory results with respect to air resistance and capacity areobtained only when thermoplastic polyurethane is used and thatrelatively high polymer components (ca. 20% of mass) are needed.

The disadvantages of prior art solutions lie in the fact that when thepolymer and adsorbent particles are mixed, the phase distribution isalways non-uniform for subsequent processing, and this has a strongadverse effect on the quality especially with respect to air resistanceand product capacity.

Thermoplastic viscid polyurethanes are known for the technicaldifficulties associated with treating them and for an enormous costfactor in using them. The polymers generally make up 20% of theproduct's mass and melting them results in considerable coverage of theadsorbent surface, which leads to significant losses in capacity and anincrease in volume resistance. Moreover, suitable spraying of thethermoplastic polyurethane on the activated product also covers theactive surface to a not inconsiderable extent and thereby reducescapacity.

DE Al 195 14 887 describes a solution for producing an adsorptive,pliable, filter surface structure on the basis of a flexible surfacestructure and polyolefins, among other things, are specified but notelaborated upon for binding the adsorbent particles. On account of thetextile substrate material, the solution is not suitable for producingmolded bodies of different shapes and is not comparable with thesolution of the present invention, which does not need substratematerials. The solution proposed in DE Al 42 38 142 contains porousbodies having adsorptive properties and mentions polyolefins as thebinding agent but does not elaborate. The adsorbent particles andbinding agent particles which it describes are of comparable sizes, sothis does not compare with the solution of the present invention due todifferent separation problems.

A need has thus been recognized to develop a polymer-bonded granularadsorptive, absorptive, chemisorptive, or catalytically active materialwhich is capable of forming an open-pore and sorptive foamed body atincreased temperatures while not reducing the specific surface of theactive material, and with a binding effect only during the mixing andprocessing phases, as well as a process for producing molded bodies fromthis material.

A need has also been recognized to develop an adsorptive, absorptive,chemisorptive, or catalytically active material and a technologicalprocess for producing molded bodies from this material which overcomethe disadvantages of the prior art and achieve higher capacity, simplerprocessing, and minimized costs for at least the same degree ofmechanical stability.

SUMMARY OF THE INVENTION

The aforementioned needs have been met with an unanticipated solution,in that a thermoplastic polymer with a slight amount of coverage on thesurface of the active material was found along with a suitable bindingagent by which optimal uniform distribution of the granularthermoplastic polymers in the active material is ensured and the polymerparticles are bound to the granular active material for longer periodsof processing, while minimizing the wetting of the material's activesurface with the binding agent entering a chemically inert state duringthe hardening process and thus minimizing reduction in capacity for theactive material.

Low-density polyethylene with a low melting point was determined by theinvention to be a low-coverage thermoplastic polymer on activematerials. The polyethylene enables a strong mechanical binding effectamong the particles of the active material, allowing mechanicaloperations, such as sawing, grinding, drilling, etc., on the finishedmolded bodies.

The active surface of the active material is only minimally covered (<2%loss of specific surface). A polymer amount as low as 5% by mass of theactive material enables sufficient mechanical stability of the moldedbodies for certain uses. The problem of efficient uniform distributionof the thermoplastic polymers in the active material over long periodsof processing was solved by using a fixing agent (or binding agent)having a modified amino resin oligocondensate basis (or backbone). Amelamine resin precondensate partially etherified with methanol andmodified and neutralized with triethanolamine is especially advantageousfor wetting the thermoplastic polymers with the aminoplast, for bindingto the active material while minimally wetting it, and for inertbehavior following the thermal process. During the thermal treatment,the amino resin precondensate cross-links to a polymethylene melaminewhile forming an open-pore, foam-like polymer with good sorptiveproperties due to its high specific surface (up to 300 m²/g). Thesesorptive properties extend to gases, ions, and other chemical speciessuch as oils, solvents, etc.

The fixing or binding agent used thus contributes to the creation ofsorptive surfaces. It is important to use binding systems which containno organic solvents, i.e. to use water-dilutable amino resinprecondensates.

If binding systems which contain organic solvents are used, the solventcomponents are instantaneously adsorbed on the active material, thebinding or fixing components become dry, and the above-mentionedseparation of components affects all subsequent processing.Water-dilutable systems, however, remain in a viscid, flowable state forat least 120 minutes and thus can be easily processed over this periodof time.

Experiments were run, for example, in which low-pressure polyethylene inparticulate form (e.g. M_(W) 35,000; M_(N) 7,700) with a melting pointbetween 85 and 140° C. was mixed with a melamine resin precondensate ina suitable container with a stirring apparatus. When the polyethylene isthoroughly mixed and wetted with the amino resin precondensate, agranular activated carbon, for example, is added and intensive mixingcontinues until homogenous. The mixture is then passed into a suitablemolding device and formed at low pressures and temperatures ofapproximately 100° C. During this procedure, the amino resin componentsfoam, cross-link, and cure, and at the same time the polyethylene bodymelts as polymer bridges are formed between the individual grains ofactivated carbon. When cooled for a brief period of time and releasedfrom the mold, the result is a molded body which can undergo mechanicalprocessing.

DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The following examples are intended to illustrate but not limit theinvention.

EXAMPLE 1

Producing a melamine resin precondensate. 279 ml of formalin (30% mass,aqueous) are brought to pH 9 with a diluted sodium hydroxide solutionand heated to a temperature of 80° C. Then 63 grams of melamine(striaminotriazine) are added. The temperature rises to 94° C. duringthe reaction. When the melamine has been completely dissolved, thesolution is cooled to 60° C. Here, clouding may occur due to methylolcompound deposits. At 60° C., 270 ml of methanol and 1.6 ml of ahydrochloric acid and water mixture in a 1:1 ratio are added and allowedto reflux at this temperature for approximately 20 to 30 minutes. Then6.3 grams of triethanolamine are added and a methanol-water mixture isdistilled out azeotropically at 60° C. under vacuum conditions (approx.15 torr) until a solid content of approx. 45% remains, after which 13.5grams of urea are added for stabilization.

After cooling, the resulting precondensate can be stored very well andpossesses the required properties for the purposes here described.

EXAMPLE 2

Producing the reaction mixture. In a suitable container with a stirringor agitation apparatus, e.g. 7.5 grams of polyethylene (fine-grained,melting point 90-95° C.) and 5 grams of the amino resin precondensateaccording to example 1 are subjected to intensive mixing. Then 150 gramsof activated carbon are added and intensive mixing is continued untiluniformity and good flow capacities are evident. The product is passedto a suitable device, heated to 110° C. and molded at a pressure of from0.0125 to 0.25 bar/cm². This generates e.g. molded bodies with a heightof between 25 and 50 mm depending on the molding pressure used and adiameter of 105 mm.

EXAMPLE 3

The procedure is the same as in example 2, but 15 grams of polyethyleneare used.

EXAMPLE 4

The procedure is the same as in example 2, but 15 grams of amino resinprecondensate are used.

It will be appreciated that the inventive chemical compositionsdescribed and covered herein can find a wide variety of uses. Such usesinclude, but are not limited to, use in gas masks, gas filters, aircleaners and air purifiers.

It will be appreciated that the inventive chemical compositionsdescribed and covered herein can serve a wide variety of functions, notthe least of which is the filtering of gases, including the filtering ofnoxious gases.

In recapitulation, at least one presently preferred embodiment of thepresent invention broadly contemplates polymer-bonded granularadsorptive, absorptive, chemisorptive, or catalytically active material,characterized by the fact, that an adsorptive, absorptive,chemisorptive, or catalytically active fine-grained material is mixedwith a finely particulate, meltable polyethylene with the addition of abinding agent having an oligocondensate basis and processed.

Additionally, at least one presently preferred embodiment of the presentinvention broadly contemplates polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active materialcharacterized by the fact, that the finely particulate polyethylenewhich is used is preferably a low-density polyethylene.

Furthermore, at least one presently preferred embodiment of the presentinvention broadly contemplates polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active materialcharacterized by the fact, that the finely particulate polyethylene hasa melting range of 85 to 130° C., preferably 90 to 115° C.

Additionally, at least one presently preferred embodiment of the presentinvention broadly contemplates polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active material,characterized by the fact, that the finely particulate polyethylene hasa particle size of from {fraction (1/10)} to ½, preferably from ⅛ to ¼,of the particle size of the granular adsorptive, absorptive,chemisorptive, or catalytically active material.

Furthermore, at least one presently preferred embodiment of the presentinvention broadly contemplates polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active material,characterized by the fact, that the polyethylene is added at 5 to 30%,preferably 7 to 20% of the mass of the granular adsorptive, absorptive,chemisorptive, or catalytically active material.

Additionally, at least one presently preferred embodiment of the presentinvention broadly contemplates polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active material,characterized by the fact, that the binding agent used is an amino resinprecondensate.

Furthermore, at least one presently preferred embodiment of the presentinvention broadly contemplates polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active material,characterized by the fact, that the binding agent used is an aqueousamino resin precondensate modified with triethanolamine and methanol.

Additionally, at least one presently preferred embodiment of the presentinvention broadly contemplates polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active material,characterized by the fact, that the quantity of binding agent is 10 to80%, preferably 30 to 50% of the mass of the polyethylene used.

Finally, but not necessarily exclusively, at least one presentlypreferred embodiment of the present invention broadly contemplates aprocess for producing molded bodies of a polymer-bonded granularadsorptive, absorptive, chemisorptive, or catalytically active material,characterized by the fact, that: the meltable polyethylene isintensively wetted with the oligocondensate in a suitable mixingcontainer; the fine-grained adsorptive, absorptive, chemisorptive, orcatalytically active material is added; the mixture undergoes intensivemixing; the mixture is conveyed via a suitable transport system to aprocessing machine; the mixture is formed into a body in the mold attemperatures of 90 to 180° C., preferably 100 to 140° C. and atpressures of 0.0125 to 0.25 bar/cm², preferably 0.0225 to 0.0625bar/cm²; the molded body is cooled in the mold and then released fromthe mold.

If not otherwise stated herein, it may be assumed that all componentsand/or processes described heretofore may, if appropriate, be consideredto be interchangeable with similar components and/or processes disclosedelsewhere in the specification, unless an express indication is made tothe contrary.

If not otherwise stated herein, any and all patents, patentpublications, articles and other printed publications discussed ormentioned herein are hereby incorporated by reference as if set forth intheir entirety herein.

It should be appreciated that the apparatus and method of the presentinvention may be configured and conducted as appropriate for any contextat hand. The embodiments described above are to be considered in allrespects only as illustrative and not restrictive. The scope of theinvention is defined by the following claims rather than the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. Polymer-bonded granular adsorptive, absorptive,chemisorptive, or catalytically active material, wherein an adsorptive,absorptive, chemisorptive, or catalytically active fine-grained materialis mixed with a finely particulate, meltable polyethylene with theaddition of a binding agent distinct from said fine-grained material andsaid polyethylene, suitable for binding said polyethylene with saidfine-grained material and having an oligocondensate basis, and processedvia heating.
 2. Polymer-bonded granular adsorptive, absorptive,chemisorptive, or catalytically active material according to claim 1,wherein the finely particulate polyethylene which is used is alow-density polyethylene.
 3. Polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active material according toclaim 2, wherein the finely particulate polyethylene has a melting rangeof 85 to 130° C.
 4. Polymer-bonded granular adsorptive, absorptive,chemisorptive, or catalytically active material according to claim 3,wherein the finely particulate polyethylene has a particle size of from{fraction (1/10)} to ½ of the particle size of the granular adsorptive,absorptive, chemisorptive, or catalytically active material. 5.Polymer-bonded granular adsorptive, absorptive, chemisorptive, orcatalytically active material according to claim 4, wherein thepolyethylene is added at 5 to 30% of the mass of the granularadsorptive, absorptive, chemisorptive, or catalytically active material.6. Polymer-bonded granular adsorptive, absorptive, chemisorptive, orcatalytically active material according to claim 5, wherein the bindingagent used is an amino resin precondensate.
 7. Polymer-bonded granularadsorptive, absorptive, chemisorptive, or catalytically active materialaccording to claim 6, wherein the binding agent used is an aqueous aminoresin precondensate modified with triethanolamine and methanol. 8.Polymer-bonded granular adsorptive, absorptive, chemisorptive, orcatalytically active material according to claim 7, wherein the quantityof binding agent is 10 to 80% of the mass of the polyethylene used. 9.Polymer-bonded granular adsorptive, absorptive, chemisorptive, orcatalytically active material according to claim 4, wherein the finelyparticulate polyethylene has a particle size of from ⅛ to ¼ of theparticle size of the granular adsorptive, absorptive, chemisorptive, orcatalytically active material.
 10. Polymer-bonded granular adsorptive,absorptive, chemisorptive, or catalytically active material according toclaim 5, wherein the polyethylene is added at 7 to 20% of the mass ofthe granular adsorptive, absorptive, chemisorptive, or catalyticallyactive material.
 11. Polymer-bonded granular adsorptive, absorptive,chemisorptive, or catalytically active material according to claim 6,wherein the binding agent used is an amino resin precondensate. 12.Polymer-bonded granular adsorptive, absorptive, chemisorptive, orcatalytically active material according to claim 8, wherein the quantityof binding agent is 30 to 50% of the mass of the polyethylene used. 13.Polymer-bonded granular adsorptive, absorptive, chemisorptive, orcatalytically active material according to claim 3, wherein the finelyparticulate polyethylene has a melting range of 90 to 115° C. 14.Polymer-bonded granular adsorptive, absorptive, chemisorptive orcatalytically active material according to claim 1, whereby less than 2%of the active surface of the adsorptive material is lost. 15.Polymer-bonded granular adsorptive, absorptive, chemisorptive orcatalytically active material according to claim 1, wherein said bindingagent is water-soluble.
 16. Polymer-bonded granular adsorptive,absorptive, chemisorptive or catalytically active material according toclaim 1, wherein said fine-grained material is adapted to bind to andfilter filterable gases.
 17. Polymer-bonded granular adsorptive,absorptive, chemisorptive or catalytically active material according toclaim 16, wherein said fine-grained material comprises granularactivated carbon.
 18. Polymer-bonded material for assisting in thefiltration of filterable gases, said material comprising an adsorptive,absorptive, chemisorptive or catalytically active fine-grained materialthat has been mixed with polyethylene, with the addition of a bindingagent distinct from said fine-grained material and said polyethylene,suitable for binding said polyethylene with said fine-grained material,and processed via heating; said fine-grained material being adapted tobind to and filter filterable gases.
 19. The material according to claim18, wherein said polyethylene comprises a finely particulate andmeltable polyethylene.
 20. The material according to claim 18, whereinsaid binding agent has an oligocondensate basis.
 21. The materialaccording to claim 18, whereby less than 2% of the active surface of theadsorptive material is lost.
 22. The material according to claim 18,wherein said binding agent is water-soluble.
 23. The material accordingto claim 18, wherein said polyethylene comprises a finely particulate,meltable polyethylene.
 24. The material according to claim 23, whereinsaid fine-grained material comprises granular activated carbon. 25.Polymer-bonded granular adsorptive, absorptive, chemisorptive, orcatalytically active material, wherein: an adsorptive, absorptive,chemisorptive, or catalytically active fine-grained material is mixedwith a finely particulate, meltable polyethylene with the addition of abinding agent having an oligocondensate basis and heated; the finelyparticulate polyethylene which is used is a low-density polyethylene;the finely particulate polyethylene has a melting range of 85 to 130°C.; the finely particulate polyethylene has a particle size of from{fraction (1/10)} to ½ of the particle size of the granular adsorptive,absorptive, chemisorptive, or catalytically active material; thepolyethylene is added at 5 to 30% of the mass of the granularadsorptive, absorptive, chemisorptive, or catalytically active material;the binding agent used is an aqueous amino resin precondensate modifiedwith triethanolamine and methanol; and the quantity of binding agent is10 to 80% of the mass of the polyethylene used.
 26. Polymer-bondedgranular adsorptive, absorptive, chemisorptive or catalytically activematerial according to claim 25, wherein said fine-grained material isadapted to bind to and filter filterable gases.
 27. Polymer-bondedgranular adsorptive, absorptive, chemisorptive or catalytically activematerial according to claim 26, wherein said fine-grained materialcomprises granular activated carbon.